1. Field of Invention
The present invention relates to a non-axial type of magnetic coupling transmission system. More particularly, the present invention relates to an optimization method for a bi-axial magnetic gear system.
2. Description of Related Art
Gravitational force, electric force and magnetic force are three natural forces that can act at a distance. Through recent advances in the science field, not only has more knowledge been gained about the above physical phenomena, but also use of their characteristic properties has been applied in beneficial technical applications. Considering the use of magnetic forces, related technologies such as magnetic levitation and magnetic bearings are growing. Many practical applications for the magnetic forces are known including magnetically levitated trains, hydrodynamically operated machines, and so on. Conventional mechanical gears that are normally used in machines also have a magnetic counterpart in the magnetic gears. (refer to U.S. Pat. No. 3,936,683).
There are a number of advantages in using magnetic gears over the conventional mechanical gears. For example, mechanical gears can generate much vibration and noise during operation, whereas magnetic gears significantly reduce such vibration and noise. Furthermore, the rotating gears need lubrication and inspection for wear and tear from time to time. Therefore, if the gears can operate in a non-contact fashion, all those problems caused by friction, wear, vibration and noise disappear. Moreover, such non-contact gears are almost maintenance-free.
A magnetic gear system has at least the following advantages over the conventional mechanical gear system, namely:
1. Non-contact operation: can eliminate problems due to friction and wear, thus resulting in a longer life, easy maintenance, and great reduction of noise and vibration. PA1 2. Operation in special environments: no lubrication is needed; therefore, it can be used in a vacuum, a dust free chamber or an environment filled with uncommon gases. PA1 3. Potential for future development: with advances in electrical and mechanical engineering technologies, the range of applications for magnetic gear system is unlimitedly increasing.
Principally, magnetic gears operate through the interaction of magnetic field set up between two magnetic gears, and torque is transmitted by their mutual attraction and repulsion due to a magnetic coupling. Most conventional magnetic gear systems are designed for the coaxial type, because large torque can be transmitted. (e.g., U.S. Pat. No. 5,204,572 shows coaxial magnetic rings for load transmission.) An attempt has also been made to replace one of the magnetic rings with an electromagnet in order to attain a higher magnetic coupling. Because the magnetic coupling is achieved by the action of an electromagnet, problems, such as winding space and control current, must also be considered. Therefore, this type of magnetic gear design becomes rather complicated.
Nevertheless, since the torque transmitted through a coaxial magnetic gear system is provided by mutual interactions involving all the magnets in the two magnetic rings, a large torque can be transmitted by the coaxial magnetic system. In a non-coaxial gear system, only a few of the neighboring magnets are involved in the mutual interactions, hence weakening the resulting torque. However, due to directional restrictions of a coaxial type of magnetic gear transmission system, non-coaxial type of magnetic gear transmission system cannot be completely replaced with the coaxial type. Furthermore, the recent advances in the material research have produced a number of powerful magnets, such as a strong magnetic compound known as neodymium iron boron (NdFeB). Therefore, non-coaxial magnetic gear systems have practical value.